Vibration arrester for multi-element antenna arrays such as used in television and f. m.



July 1955 A. H. FEATHERSTUN ,1

VIBRATION ARRESTER FOR MULTI-ELEMENT ANTENNA ARRAYS SUCH AS USED INTELEVISION AND F. M.

Filed Oct. 12. 1951 INVENTOR APTHUE H. F634 THEEJ TU/V,

United btates Patent VIBRATION STER FQR MULTI-ELEMENT ANTENNA ARRAYSSUCH AS USED IN TELE- VISION AND F. I /l.

Arthur H. Featherstun, Mount Vernon, Ill. Application October 12, U51,Serial No. 250,981 4 Claims. (Cl. 250-33) This invention relates toantenna structure, and more particularly to means for preventingexcessive vibration of the elements of antennas of the type employed fortelevision and frequency modulation reception.

A main object of the invention is to provide novel and improved meansfor damping the vibration of the elements of antennas, such as theelements employed in television and frequency modulation antennas, saidmeans being very simple in construction, being easy to install,involving a minimum amount of modification of existing structures, andproviding effective damping of the vibration which would otherwise occurin the elements, whereby damage and breakage of the elements areavoided.

A further object of the invention is to provide an improved vibrationarresting means for the elements of antennas, such as television andfrequency modulation antennas, said means involving inexpensivecomponents, being adaptable for fabrication on the elements at the timeof manufacture, or for clamping on existing antenna elements, andproviding an effective arrangement for preventing excessive vibration ofthe elements, whereby bending and breakage to said elements is preventedand the etficiency of the antenna is maintained over long periods oftime without requiring repair or servicing.

Further objects and advantages of the invention will become apparentfrom the following description and claims, and from the accompanyingdrawings, wherein:

Figure l is a perspective View of a television antenna provided with avibration-damping means according to the present invention;

Figure 2 is an enlarged cross-sectional view taken on the line 2-2 ofFigure l, and showing the specific structure involved in the vibrationdamping means;

Figure 3 is a side elevational view of the structure of Figure 2;

Figure 4 is a cross-sectional view taken on the line 4-4 of Figure 3;

Figure 5 is an end elevational view of the structure of Figures 2 and 3;

Figure 6 is a longitudinal cross-sectional view taken through a modifiedform of vibration-damping means according to the present invention,which may be employed on the elements of an existing antenna, or whichmay be optionally installed on the elements during the manufacture ofthe antenna;

Figure 7 is a side elevational view of a further modified form ofvibration-damping means especially adapted to be installed on existingantennas and showing the manner of connection of the vibration-dampingmeans to an element of an existing antenna;

Figure 8 is a cross-sectional view taken on the line 88 of Figure 7.

Referring to the drawings, and more particularly to Figures 1 to 5, 11generally designates a television antenna structure comprising thevertical mast 12, the horizontal boom 13 clamped to the mast in theusual manner, the folded dipole 14 secured to one end of the 2,714,16lPatented July 26, 1955 boom 13 in the usual manner, and the horizontallyextending, rod-like elements 15 secured to the boom 13. As shown inFigure 1, the elements 15 are secured rigidly at their mid-portions tothe boom 13, and the respective ends of the elements are free. In thecase of the conventional antenna structure, the elements 15 are free tovibrate under wind forces or other causes, and when the vibration occursat a frequency close to the natural frequency of vibration of theelement, the amplitude of the vibration may become so excessive as tocause the element to snap oif adjacent to its point of connection to theboom 13. In this manner, a great number of elements become broken andrequire replacement, especially where the antenna is mounted at aconsiderable elevation and is exposed to heavy wind forces.

The element 15 is usually formed of hollow, tubular stock, as shown inFigure 2, and in accordance with the present invention, the element iscrimped at 16, 16, as well as at the end of the element, as shown at 17,t0 define a tubular housing element 18. Loosely mounted in the housingelement 18 is a damping weight element 19, which may comprise a shortlength of heavy gauge, rubber-covered Wire, such as No. 6 gaugerubber-covered Wire, having the copper conductor portion 20 and therubber sheath 21. The damping weight 19 may have a length of the orderof one inch, and the length of housing element 18 may be of the order oftwo and one-half inches, whereby the damping weight 19 is freely movablelongitudinaly in the housing element and is also freely movable to somedegree in a direction at right angles to its axis.

Both ends of each element 15 are similarly provided with thevibration-arresting means, as above described, whereby when the element15 tends to vibrate, the damping elements 19 in the housing portions 18at the ends of the element shift in position and prevent the freeportions of the element from vibrating at their natural resonantfrequencies. Thus, the amplitudes of vibrations of the free portions ofthe element 15 are kept reasonably low, and the stresses produced in theelement 15 as a result of such vibrations are kept below the values atwhich breakage of the element would occur.

Referring now to Figure 6, a modified form of vibration-damping means isdisclosed comprising a hollow plug element 22 of plastic material orother similar durable material formed with a reduced hollow stem portion23 having a longitudinal drain slot 30 and with a cavity 24communicating with the stem portion 23 by a passage 25. Looselypositioned in the cavity 24 is a weighted ball 26 which is free to movelongitudinally in the cavity 24, as well as in a direction transverse tothe axis thereof. The reduced tubular portion 23 of the vibrationarrester is secured in the end of the antenna element, shown at 15, andmay be secured therein in any suitable manner, as by a tight frictionalfit. The vibration-arresting means may be secured in the end of theelement 15 either during the manufacture of the antenna, or after theantenna has been installed. The operation of the device is similar tothe operation of the form of the invention disclosed in Figures 1 to 5,namely, when vibration of the free portions of the element 15 occur, theweight element 26 shifts its position in the cavity 24 and prevents thefree portions of the element from vibrating at their natural resonantfrequency.

In the form of the invention shown in Figures 7 and 8, a hollow plugelement 22 having a reduced portion 23 is clamped to the end portion ofan antenna element, shown at 35 and which is provided with opposedclamping channel elements 37, 37 engaged around the reduced portion 23'of the vibration arrester. Plug element 22' is formed with alongitudinal drain slot 30', as shown. A clamping bolt 38 is providedfor exerting the required clamping pressure on the reduced portion 23 torigidly secure the vibration-arresting device to the end portion of thehorizontally extending antenna element 35. As in the previousembodiments of the invention, when the element 35 begins to vibrate, theweighted ball 26 inside the housing portion 22' shifts its position andprevents the element from vibrating continuously at its natural resonantfrequency. This maintains the amplitude of vibration at a low value andprevents breakage of the element, as above described.

While certain specific embodiments of an improved vibration-arrestingmeans for the free element portions of television and frequencymodulation antennas have been disclosed in the foregoing description, itwill he understood that various modifications within the spirit of theinvention may occur to those skilled in the art. Therefore, it isintended that no limitations be placed on the invention except asdefined by the scope of the appended claims.

What is claimed is:

1. In a multi-element antenna array, the combination of a horizon-tallyextending element having at least one free end, and vibration dampingmeans comprising a housing rigidly secured to said free end and havingan internal cavity extending in. the same direction as said element, anda movable damping weight contained in said cavity, said Weightcomprising a unitary body having a volume which occupies a substantialportion of the volume of said cavity but which is substantially smallerboth longitudinally and transversely than said cavity,

whereby the weight is free to move both transversely and longitudinallyin the cavity.

2. In a. multi-element antenna. array, the combination of a horizontallyextending element having free ends, respective elongated housingsrigidly secured to said free ends and having internal cavities extendingin the same direction as said. element, and respective damping weightsmovably disposed in said cavities for free movement therein, each ofsaid weights. comprising. a unitary body having a volume which.occupies. a substantial portion of the volume of itsv respective. cavitybutwhich. is substantially smaller both longitudinally and transverselythan said cavity, whereby the weights are free to move both transverselyand longitudinally in the cavities.

3. In a multi-element antenna array of the character described, thecombination of a horizontally extending boom, a horizontal elementrigidly secured at its mid portion to said boom, respective tubularhousings rigidly carried at the ends of said element and having internalcavities extending in the same direction as said element, and respectivedamping weights loosely disposed in said housings for free movementtherein, each of said weights comprising a unitary body having a volumeWhich occupies a substantial portion of the volume of its respectivecavity but which is substantially smaller both longitudinally andtransversely than said cavity, whereby the weights are free to move bothlongitudinally and transversely in the cavities.

4. in a multi-element antenna array, the combination of a horizontallyextending boom, 2. horizontal element rigidly secured at its mid portionto said boom, respective tubular housings rigidly carried at the endsof. said element and having internal cavities extending in the samedirection as said element, and respective elongated damping weightsloosely disposed in said housings for free movement therein, each Weightcomprising a unitary body having a volume which occupies a substantialportion of the volume of its respective cavity but which issubstantially smaller both longitudinally and transversely than saidcavit whereby the weights are free to move both longitudinally andtransversely in the cavities.

References Cited in the file of this patent UNITED STATES PATENTS2,155,052 Byland' Apr. 18, 1939 2,195,041 Von- Schlippe' Mar. 26, 19402,302,670 Buchanan Nov. 24, 1942 2,462,961 Harker Mar. 1, 1949 2,586,043Hodgson-et al Feb. 19, 1952 FOREIGN PATENTS 652,318 Great Britain Apr. 18-, 1951

